Extremely Slow, or Non-Existent Internet Connection

I just got a brand-new 13" Macbook Air today. The Internet connection is either EXTREMELY slow or seems to just not work at all on websites that are more exhaustive than Google (which isn't to say much...)

What on earth is going on? It is definitely just an issue with the Mac. I have a 5-year old VAIO laptop and numerous PC desktops around the house, all working infinitely faster.

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